1. Technical Field
The technology described in this patent application is generally directed to the field of software performance analysis and diagnostics. More specifically, the technology provides a system and method for detecting redundant subroutine calls in software applications.
2. Description of the Related Art
Complex software applications typically comprise hundreds or even thousands of subroutines or functions, each of the subroutines typically performing a particular function or set of functions. The subroutines of the software application communicate with one another by calling one another in a variety of distinct calling paths. A call path is a communication path between two or more subroutines. Oftentimes, the calling paths in complex applications can become redundant as between two subroutines, meaning that there are several communication paths between the subroutines.
In order to visualize theses calling paths, a call tree is often developed. The call tree is a tree representation of all the software subroutines that are called while a program is executing. Within the call tree, each subroutine is represented by a node, and links between the nodes represent call paths. Several commercially available software performance analysis and diagnostic tools are available that can generate such a calling tree, such as Rational Quantify™ and Intel Vtune™, for example. This call tree data can be expressed as: (i) routine x was called; (ii) routines a and b called x; (iii) routine x calls routines c, d, and e; and (iv) repeat the above sequence (i)-(iii) for each routine in the call path.
By using this call tree data, a complete call path for every routine of the program under analysis can be generated. The number of times that a routine is called, and how often it is called within a particular call path may also be generated along with the call tree data. By analyzing the data in the call tree, a performance analyst may be able to identify a performance bottleneck.
FIG. 1 is an example call path diagram 10 showing the execution path between four functional software routines or nodes of an exemplary computer program. In this diagram, the four nodes—afoo 12, bfoo 14, cfoo 16, and foo 18—communicate with one another through a particular set of execution paths. In this example, the software routine afoo 12 makes a direct call to bfoo 14, cfoo 16 and foo 18. In addition, the routine bfoo 14 makes a direct call to foo 18 and cfoo 16, which in turn makes another direct call to foo 18. Thus, the routine afoo 12 makes four calls to the routine foo 18, one direct call, and three indirect calls through the functions bfoo 14 and cfoo 16. This relationship between afoo and foo is generally termed redundant because of the plurality of calling paths between the two functions.
Upon determining the redundant relationship between afoo 12 and foo 18, a performance analyst may determine that a majority of the execution time was spent in foo 18, and then a software developer may attempt to rewrite the foo 18 routine to make it faster. Alternatively, the software developer may change afoo 12 to call foo 18 only once, and then cache the data returned therefrom and pass it along to bfoo 14 and cfoo 16 so as to eliminate the need for these routines to make another call to foo 18, thereby eliminating any redundancy.
Although this may seem like a straightforward approach to fixing the performance problem, in reality these redundant situations are very difficult to detect and diagnose using the commercially available performance analysis tools. Because a typical software application may have hundreds or more of inter-related routines, the resulting calling path data and call trees may become extremely difficult to analyze. Moreover, in determining how a particular function is performing, it is necessary to understand and analyze the calling path of any parent functions. The commercially available tools do not provide sufficient intelligence or functionality to enable this type of problem to be diagnosed by the performance analyst or the software developer.